The present invention is concerned with electrical multiway connectors.
Our U.K. Patent Application No. 2 205 201A shows that capacitive and inductive elements may be mounted within a multiway circular connector in such a way that the ceramic capacitor elements are not subjected to the mechanical stresses of mating two parts of a multiway connector.
Our European Patent Application publication No. 0 399 802 shows that spring contacts associated with each filter may further reduce assembly and intermating stresses within such integrated assemblies.
The capacitor and capacitor/inductor filter elements described in the above-mentioned applications provide protection to vulnerable electronic circuitry against the effects of electromagnetic interference (emi), by providing a series impedance or shunt admittance to interference currents which would otherwise be conducted to the vulnerable circuitry. However, such circuit elements provide only limited protection against voltage transients, caused for example by lightning strikes. This limited protection results only when the risetime of the voltage spike is sufficiently short that the (Fourier equivalent) frequency content of the spike is correspondingly high enough for the capacitor element of the filter to provide an effective by-pass to ground.
Additional protection is needed in such cases, to limit both the maximum voltage and total energy transmitted to the vulnerable circuitry within the enclosure to be protected. Such protection commonly takes the form of a further shunt element, such as a varistor or transient absorbing diode. Such elements are reverse voltage breakdown devices, providing a low resistance to ground under high voltage excursion conditions. Typical limiting conditions of operation include maximum pulse current and total dissipated energy.
However, due to their inherently high series impedance, such so-called `transient absorbing` elements are not effective as high frequency filter elements where a low impedance to ground is required at frequencies from a few tens of kHz to in excess of 1 GHz. Therefore, combinations of feedthrough filter elements and transient absorbing elements are required to protect vulnerable electronic circuitry from both the destructive effects of high frequency electromagnetic interference conducted on wires passing into the equipment, and the destructive effects of typically lightning-induced conducted voltage/current transients.
Whilst transient absorbing elements are readily available and may be mounted on a printed circuit board mounted within an equipment, this utilises a large amount of space. In addition, in such known arrangements, the filter elements when mounted in the connectors may receive stress themselves from the incoming voltage transient.
It would thus be desirable to provide a single connector assembly which contains both transient absorption elements and rfi suppression filters. Whilst transient absorbing elements may be mounted in chip form upon the termination itself, the space available severely limits the device size and its current/energy handling ability.